Comprehensive Investigation of Airborne Benzalkonium Ion Behavior Following Nebulization: Implications for Indoor Air Quality and Health Risk Assessment

The COVID-19 pandemic has intensified the use of quaternary ammonium compound (QAC) disinfectants, raising concerns about potential health effects. This study investigated the airborne behavior of benzalkonium chloride (BKC), a common QAC, sprayed at 500 ppm for 4 min in a 105 m³ space using automatic and manual methods. Airborne BKC was collected via an air pump and quantified using LC-ESI-MRM/MS. Results showed that BKC concentrations peaked during spraying but rapidly decreased thereafter, becoming negligible within 8–12 min postspraying. Cumulative capture exhibited a sigmoidal trend with time, with maximum captures of 8.21 μg (front) and 1.36 μg (back) for automatic spraying, and 0.14 μg (front) and 0.29 μg (back) for manual spraying. The “exposure to spray model” was applied to determine parameters such as airborne fraction and settling velocity. Hazard quotients (HQs) were calculated based on the maximum cumulative captures, with all values remaining below 1, indicating minimal health risks. Specifically, for the automatic sprayer, HQs were 0.856 (front) and 0.142 (rear), while for the manual sprayer, they were 0.015 (front) and 0.030 (rear). The highest HQ of 0.856, observed for automatic spraying at the front location, suggests that some caution may be warranted in this scenario. The study demonstrates that while BKC concentrations can be significant during spraying, they decrease rapidly postapplication, leading to limited exposure risks. These findings provide valuable insights into the safe use of QAC disinfectants and their impact on indoor air quality, particularly relevant in the context of increased disinfectant practices during the COVID-19 pandemic.